Hi Christian, I love your patch! Yet something to improve: [auto build test ERROR on 3cea11cd5e3b00d91caf0b4730194039b45c5891] url: https://github.com/0day-ci/linux/commits/Christian-Brauner/fs-idmapped-mo... base: 3cea11cd5e3b00d91caf0b4730194039b45c5891 config: x86_64-randconfig-a003-20201115 (attached as .config) compiler: clang version 12.0.0 (https://github.com/llvm/llvm-project 9a85643cd357e412cff69067bb5c4840e228c2ab) reproduce (this is a W=1 build): wget https://raw.githubusercontent.com/intel/lkp-tests/master/sbin/make.cross -O ~/bin/make.cross chmod +x ~/bin/make.cross # install x86_64 cross compiling tool for clang build # apt-get install binutils-x86-64-linux-gnu # https://github.com/0day-ci/linux/commit/34d901623d75c52a3360155d3f5a8f838... git remote add linux-review https://github.com/0day-ci/linux git fetch --no-tags linux-review Christian-Brauner/fs-idmapped-mounts/20201115-185706 git checkout 34d901623d75c52a3360155d3f5a8f8389d3dc29 # save the attached .config to linux build tree COMPILER_INSTALL_PATH=$HOME/0day COMPILER=clang make.cross ARCH=x86_64 If you fix the issue, kindly add following tag as appropriate Reported-by: kernel test robot <lkp(a)intel.com&gt; All errors (new ones prefixed by >>): In file included from <built-in>:1: __u64 attr_set; ^ ./usr/include/linux/mount.h:126:2: error: unknown type name '__u64' __u64 attr_clr; ^ ./usr/include/linux/mount.h:127:2: error: unknown type name '__u64' __u64 propagation; ^ 3 errors generated. --- 0-DAY CI Kernel Test Service, Intel Corporation https://lists.01.org/hyperkitty/list/kbuild-all@lists.01.org